All antennas are equipped with dual polarization receivers for the 3mm, 2mm, 1.3mm, and 0.8mm atmospheric windows. The frequency ranges are 80GHz to 116GHz for the 3mm band, 129GHz to 174GHz for the 2mm band, 201 to 267GHz for the 1.3mm band, and 277 to 371GHz for the 0.8mm band.
Each band of the receivers is dual-polarization with the two RF channels, one per polarization, of one band observing at the same frequency. The four different bands are not co-aligned in the focal plane (and therefore on the sky). Due to the pointing offsets between the different frequency bands, only one band can be observed at any time. One of the three other bands is in stand-by mode (power on and local oscillator phase-locked) and is available, e.g., for pointing. Time-shared observations between different RF bands (e.g. band 1 and band 3) are possible in well justified cases, they are however not very efficient.
The mixers for bands 1, 2, and 3 are single-sideband, backshort-tuned; they will usually be tuned LSB, except for the upper part of the frequency range in all three bands where the mixers will be tuned USB. The band 4 mixers are 2SB receivers, operated in SSB mode. They can be tuned LSB or USB throughout most of the accessible frequency range. The typical image rejection is 10dB (20dB for band 4). Each IF channel is 3.6GHz wide (4.2-7.8GHz).
The two IF-channels (one per polarization), each 3.6GHz wide, are transmitted by optical fibers to the central building.
The wide-band correlator WideX is able to process both 3.6GHz wide IFs simultaneously with a fixed resolution of about 2MHz. The narrow-band correlator can process the two 3.6GHz wide IF-channels (one per polarization) only partially. A dedicated IF processor converts selected 1GHz wide slices of the 4.2-7.8GHz first IFs down to 0.1-1.1GHz, the input range of the narrow-band correlator. Further details are given in Section describing the correlator setup and the IF processor.
|Band 1||Band 2||Band 3||Band 4|
|/[dB]||-10||-12 ... -10||-12 ... -8||-20|